wayland: only render if we have frame callback

Back in the olden days, mpv's wayland backend was driven by the frame
callback. This had several issues and was removed in favor of the
current approach which allowed some advanced features (like
display-resample and presentation time) to actually work properly.
However as a consequence, it meant that mpv always rendered, even if the
surface was hidden. Wayland people consider this "wasteful" (and well
they aren't wrong). This commit aims to avoid wasteful rendering by
doing some additional checks in the swapchain. There's three main parts
to this.

1. Wayland EGL now uses an external swapchain (like the drm context).
Before we start a new frame, we check to see if we are waiting on a
callback from the compositor. If there is no wait, then go ahead and
proceed to render the frame, swap buffers, and then initiate
vo_wayland_wait_frame to poll (with a timeout) for the next potential
callback. If we are still waiting on callback from the compositor when
starting a new frame, then we simple skip rendering it entirely until
the surface comes back into view.

2. Wayland on vulkan has essentially the same approach although the
details are a little different. The ra_vk_ctx does not have support for
an external swapchain and although such a mechanism could theoretically
be added, it doesn't make much sense with libplacebo. Instead,
start_frame was added as a param and used to check for callback.

3. For wlshm, it's simply a matter of adding frame callback to it,
leveraging vo_wayland_wait_frame, and using the frame callback value to
whether or not to draw the image.

1 files changed, 2 insertions, 4 deletions

diff --git a/video/out/wayland_common.h b/video/out/wayland_common.h
index 7eec7be2d5..27f4f87b0e 100644
--- a/video/out/wayland_common.h
+++ b/video/out/wayland_common.h
@@ -110,14 +110,11 @@ struct vo_wayland_state {
     /* Presentation Feedback */
     struct vo_wayland_sync *sync;
     int sync_size;
-    int64_t user_sbc;
     int64_t last_ust;
     int64_t last_msc;
-    int64_t last_sbc;
-    int64_t last_sbc_mp_time;
-    int64_t vsync_duration;
     int64_t last_skipped_vsyncs;
     int64_t last_queue_display_time;
+    int64_t vsync_duration;
 
     /* Input */
     struct wl_seat     *seat;
@@ -154,6 +151,7 @@ void vo_wayland_uninit(struct vo *vo);
 void vo_wayland_wakeup(struct vo *vo);
 void vo_wayland_wait_events(struct vo *vo, int64_t until_time_us);
 void vo_wayland_wait_frame(struct vo_wayland_state *wl);
+void vo_wayland_sync_clear(struct vo_wayland_state *wl);
 void wayland_sync_swap(struct vo_wayland_state *wl);
 void vo_wayland_sync_shift(struct vo_wayland_state *wl);
 void queue_new_sync(struct vo_wayland_state *wl);